Modelling the effect of yarn twist on the tensile strength of unidirectional plant fibre yarn composites

Shah, Darshil U. and Schubel, Peter J. and Clifford, Mike J. (2012) Modelling the effect of yarn twist on the tensile strength of unidirectional plant fibre yarn composites. Journal of Composite Materials, 47 (4). pp. 425-436. ISSN 0021-9983


The true structural potential of plant fibres as reinforcing agents can only be realized when the highest reinforcement efficiency is employed. Hence, aligned unidirectional plant fibre composites (PFCs) are of interest. However, due to the short length of technical plant fibres, the reinforcement needs to be in the form of staple fibre yarns which have a twisted structure. Although twist facilitates yarn processability, it has several detrimental effects on the composites produced. One of these detrimental effects is fibre obliquity and misalignment which results in a drastic drop in mechanical properties of the composite. No model is currently available to predict the effect of reinforcing yarn twist on unidirectional PFC tensile strength.
In this paper, plant fibre staple yarn structure-property relationships are discussed and a mathematical model based on i) the modified rule of mixtures for PFCs, ii) idealised twisted structure of a staple fibre yarn, and iii) Krenchel orientation efficiency factor is developed to predict the influence of yarn twist on aligned PFC strength. An orientation efficiency factor of cos2(2α), where α is the surface twist angle, is derived which can be easily substituted into the rule of mixtures for composites. The model is validated with extensive experimental data from Goutinos et al. [7] and shows strong agreement; the derived model is a near-perfect fit for the experimental data (with R2 = 0.960).
Models by other researchers on the effect of twist on elastic modulus of high-performance impregnated filament yarns are complex and found to be unsuitable to predict the effect of twist on PFC tensile strength. The Tsai-Hill model is observed to significantly over-estimate the reduction in tensile strength at low twist angles.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 31 Mar 2017 04:44
Last Modified: 31 Mar 2017 06:59
Uncontrolled Keywords: natural fibres, polymer-matrix composites, twisted yarn, modelling, reinforcement orientation efficiency, tensile strength
Fields of Research (2008): 09 Engineering > 0912 Materials Engineering > 091202 Composite and Hybrid Materials
Fields of Research (2020): 40 ENGINEERING > 4016 Materials engineering > 401602 Composite and hybrid materials
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
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